The present invention relates generally to a system for heating liquids and gases usable for various treatments inclusive of chemical treatments and washing treatments, and more particularly to a process and system comprising a unit for heating a treating liquid effectively within a reduced time of period and mixing the treating liquid uniformly within a reduced period of time.
In washing treatment steps for washing and otherwise treating surfaces of substrates with treating liquids as well as in various treatment steps making using of chemical reactions, the treating liquids are heated to increase chemical reaction rates due to said treating liquids, thereby reducing treating periods of time. In general, chemical reaction rates increase largely with increasing temperature; it is desired to increase reaction temperatures as high as possible.
FIG. 11 is a representation illustrative of one example of a conventional system making use of a chemical treating liquid.
A treating vessel 1 is filled with a treating liquid 2 up to a treating liquid level 3, wherein an article 4 to be treated is immersed in the treating liquid 2 so that the article 4 is treated with the treating liquid 2. The treating liquid 2 is fed from a reservoir 5 for receiving an overflow of treating liquid from the treating vessel via a pump 6 to a filter 7 where it is filtered. Then, the treating liquid is heated to a predetermined temperature by a heating unit 8 using an electrically heated wire or an electric bulb as a heating source, whence it is fed back to the treating vessel. The treating liquid is consumed due to its evaporation during circulation or because a portion thereof is discharged along with the article 4 from the system to the outside. In general, the treating liquid is largely consumed by the evaporation of a liquid component because it is heated to a temperature close to its boiling point. To prevent an increase in the concentration of the treating liquid due to liquid losses, a level sensor 9 is provided in the treating liquid reservoir 5 to detect a treating liquid loss due to evaporation, etc., thereby opening a diluting liquid feeding valve 10 to replenish a diluting liquid from a diluting liquid vessel 10 to the reservoir 5. On the other hand, outputs of a thermometer 12 for measuring the temperature of the treating liquid, liquid sensor 9 and the like are sent to a control 13, which in turn adjusts a diluting liquid adjusting valve 11 or the like to keep the amount and temperature of the treating liquid in predetermined ranges.
The treating vessel 1 and treating liquid reservoir 5 are heated and insulated by a heating and insulating member 14 called a rubber heater, and the treating liquid denatured in the treating vessel is discharged as a drain 15 to the outside.
When the article is treated with the treating liquid heated to its boiling point or a temperature close thereto, the amount of the treating liquid evaporated increases with an increase in the liquid component to be replenished. When the treating liquid is an aqueous solution, it is required to make up for water that is lost by evaporation. Upon the fresh liquid added to the treating liquid, however, the concentration and temperature thereof may vary. The variation in the concentration or temperature of the treating liquid may then have an adverse influence on the article 4 to be treated. For the heating unit 8 used to heat the treating liquid, a heating unit comprising a quartz tube and a nichrome wire or an electric bulb mounted therearound is ordinarily employed. However, it is required to make frequent replacements of quartz tubes to avoid possible damage to the quartz tube by heating.
When the treating liquid is heated via the quartz tube, much time is needed for heating the treating liquid. A problem with such long-term heating is the degradation of the treating liquid, etc.
A semiconductor production process in particular involves a number of treating steps using treating liquids, including the step of washing silicon wafers. Consistent treatments using treating liquids have a great influence on the properties of semiconductor devices, and treating time reductions have a great influence on productivity improvements as well.
It is therefore one object of the invention to provide a treating process and system that enable a uniform treatment using a chemical treating liquid to be achieved within a reduced period of time.
Another object of the invention is to provide a process and system that make it possible to achieve consistent yet short-term treatments in a semiconductor production process comprising steps of substrate washing, resist removal, resin layer removal, nitride or oxide film removal, and etching.